Power transmission



Jan. 5, 1943. J. ROBINSON 2,307,544

POWER TRANSMISSION Filed Mai'ch 23, 1940 2 Sheets-Sheet l M INVENTORJAMES ROBINSON BWKM ATTORNEY Jan. 5, 1943.

J. ROBINSON POWER TRANSMIS S ION Filed March 23, 1940 2 Sheets-Sheet 2INVENTOR JAMES ROBINSON W? 1 w r M 5 H2 i 6 a a Z a Z w a m 8 l 7 7 6 5F. 1 Q2 m 1 z 4 a M 6 a 4 4 a W Q 5 w H. 1 ow 6 58 2?. a a s 4L3 g a 4 47 ELF- e M. a

8 w z E e a m a 0 e 2 a m o 8 1 6 @1 Th a0 4 a n S 8 a w a 7 as 8 ATREST ATTORNEY lating devices, one of pump and another as a fluid motor.

Patented Jan; 5, 1943 James Robinson, Detro ers Incorporated, De

of Michigan it, Mich, assignor to Vicktrolt, MiGlL, a corporationApplication March 23, 1940 Serial No. 325,537

3 Claims.

to power transmissions to those of the type com- This invention relatesand more particularly prising two or more fluid pressure energy trans-'which may function as a The invention is more particularly concernedwith a hydraulic power transmission system' for op'eratinga plurality ofhydraulic motors in sequence'such as are used, for example, in ahydraulically-operated, triple-action press. It is desirable in systemsof this character to avoid the use of individual pumps for each of thefluid motors, particularly in larger machines where the large volume andhigh pressure requirements necessitate an expensive this character,where only'one pump is available to supply fluidio the motors insequence, it is found diflicult to hold pressure on' one motor which'hascompleted a stroke while the next mo tor ismoving through its stroke andencountering resistance lower than that atthe first motor.

It is an object of the present-invention to pro- V vide a hydraulicpower transmission system for pump. Immachine of operating a pluralityof fluid motors in sequence I and wherein pressure may be maintainedregardless of how low is the pressure-required to A further object thischaracter an improved auxiliary pump circuit for maintainingpressure onone motor while another motor is by the main pump.

A further object is to providea system of the operate the next motorjcharacter described whereinthe, auxiliary pump is effective both duringforward and return strokes of each motor.

Further objects and advantages of the'present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred form of the present invention is clearlyshown.

In the drawings:

Fi ure 1 is a diagrammatic view of a power transmission system embodyinga preferred form of the present invention.

Figure 2 is a circuit diagram with a table showing the positions of thevarious valves during several conditions of operation.

Referring now to Figure i there is shown three fluid motors Ill, l2 andI4, each of which is represented diagrammatically as a simplepiston-andcylinder type of motor. These motors may serve to actuate theouter slide, the inner slide, and the lower or main slide of atriple-action metaldrawing press, it being operating at a, lowerpressureonce built up at one motor is to provide-in a system of thewell-known forms of double-acting hydraulic motors conventionally usedfor presses of this character may be used in place of theform of motorillustrated.

Three pilot-operated, solenoid-controlled, directional valves areillustrated at I 6, l8 and 20. Each of these valves is provided withsimilar solenoid pilot-control assemblies, one at either end of thevalve, for shifting the,spool thereof. Each of these assemblies mayconsist ofa three-way pilot valve 22 normally spring-biased downwardlyand adapted to be lifted upon energization of the solenoidassociated'therewith at the lower end.

In its lower position the valve 22 connects its associated operatingchamber 24 with a. tank connection 26, and, when lifted to its upperposition, transfers the operating chamber 24 to communication with apilot pressureconnection 28. Suitable needle and .check valves 30 and 82may be provided for controlling the speed of movement of the spool ofthe main valve. Thus, whenever a pilot valve 22 is shifted upwardly byenergization of its associated solenoid, pilot pressure will be admittedto that end of the main valve for causing the spool thereof to shiftaway from thepilot valve which was operated; j

The valve It has a three-land spool 34 which is normallyi centered by aspring 36. The tool 34 is provided with a central bore and radialpassages for connecting the pressure port 38 with the tank ports 48 whenthe spool 34 is in its central position. The'two motor ports 4| and 43of valve it connect by conduits 42 and 44 with the opposite ends ofmotor Ill.

The valve. I8 is similar to the valve I8 except that the spool 46thereof is not provided with the central bore, and the spring-centeringmeans is omitted. It is provided with a pressure port 48,. tank ports50, and has its cylinder ports 5| and53 connected to the opposite endsof motor I 2 by conduits 52 and 54.

Valve 20 is similar to valve l8 except that one motor port 55 is plugged,yvhile the other, 51, is connected by a conduit 56 to the head endmotor l4. The rod end of the latter. connects by a conduit 58 with theconduit 54.

The tank ports 60 of valve 20 and also the tank ports 40 and of valvesl6 and 18 are connected to a suitable reservoir or tank 82 by aunderstood that anyof' conduit 64. The pressure port 66 of valve 20 andthepressure ports 38 and 48 of valves l6 and I8 are connected by adelivery conduit 68 with the discharge side of a suitable high-pressurepump 10 having sufilcient volumetric capacity to supply the requirementsofeach oi the of the motors I0, I2 and I4. may be incorporated limitingthe pressure therein to a safe value.

direct communication with I The conduit 68 is in port 66 of valve 20 andcommunicates with ports 38 and 48 of valves I6 and I8 through checkvalves I4 and I6, respectively. The solenoids for shifting the valvesI6, I8 and 20 to the right and left are designated C, -D, E, F, G, andH, respectively.

An auxiliary pump I8 of ,the high-pressure type, but having a muchsmaller volumetric capacity than pump I0, has a delivery conduit 80which extends by a branch 82 to a pressure-reducing valve 84 ofconventional construction. A suitable relief valve 8| may beincorporated in conduit 80. From the reducing valve 84 a pilot pressureconduit 86 extends to the pilot pressure connection 28 of each of thepilot valves 22. A branch delivery conduit 88 extends to the pressureport 80 of a solenoid-operated, four-wayvalve 82, the tank ports 94 ofwhich are connected to tank by a conduit 96. The valve 82 has a two-landspool 88 adapted to be shifted to the right and left, respectively, bysolenoids designated A and nects by a conduit I02 through a relief valveI04 and check valve I06 to the motor conduit 44. The discharge port ofrelief valve I04 connects by a conduit I08 with the motor conduit 52..The other motor port I I of thevalve 82 connects by a conduit II2through a relief valve 4 and check valve Il6 with the motor conduit 58.The discharge port of relief valve II4 connects by a conduit II8 withthe motor conduit 42.

For the purpose of controlling energization of the solenoids of thevarious valves an electrical circuit is provided as follows: A holdingrelay R has a normally open circuit at the bottom adapted, when closed,to establish connection between one side of a suitable power source,designated L and a conductor I20 extending to the solenoid A, the otherside of which is connected to the other side of the power source L.Relay R also has a normally closed circuitadapted to connect between 1'.and a conductor I22 extending to the solenoid B and therethrough to theline L. The relay R also has three additional sets of normallyopencontacts and a set of holding contacts. The latter connect between theoperating coil of the relay and a conductor I24 extending to one set ofnormally closed contacts B. One motor port I00 conof a limit switch LSadapted to be opened whenever the motor I4 has shifted the pistonthereof to the upper limit or its stroke.

A second holding relay R has a set of normally open contacts adapted,when closed, to connect between line L and a conductor I26 extending tothe solenoid C and therethrough to the line L. A normally closed set ofcontacts on the relay R connects between a conductor I28 and a conductorI30 extending to the solenoid D and extends from line L through anormally-closed limit switch LS adapted to be opened when the piston ofmotor I0 is at the upper limit of its stroke. The relay R also hasholding contacts which connect between the operating coil of the relayand a conductor I32 extending to a limit switch LS normally closed andadapted to be opened when the piston of motor I2 is at the upper. limitof its stroke. A branch conductor I34 also extends from conductor I32 toone of the normally-open set of contacts at relay R For the purpose ofinitially energizing relays R and RF conductors I44 and I48 extend fromthe operating coils thereof to independent contacts of a normally-open,push-button, starting switch I40 and to line L A holding relay R. hasnormally closed and. normally open contacts connecting by conductors I42and I44 with the solenoids E and F. Its holding contacts connect by aconductor I46 with one set of normally closed contacts at limit switchLS. The operating coil of relay R may be energized through a conductorI48 extending to a' I normally-open limit switch LS and from there by aconductor I50 to a second set of normally open contacts at the relay R Aholding relay R has normally open contacts and normally closed contactsconnecting by conductors I52 and I54 with the solenoids G and H,respectively. The holding contacts of relay R connect by a. conductorI56 with the third set of normally closed contacts at limit switch LSFor the purpose of energizing the coil of relay R a conductor I58extends through a normally-open limit switch LS adapted to be closedwhen the piston of motor I2 reaches the bottom of its stroke, and fromthere a conductor I60 extends to the third set of normally open contactsat relay R In operation, with the pumps 10 and 18 being driven by theirrespective prime movers and with the parts in the position illustratedin Figure 1 and in the first line of the table of Figure 2, theapparatus is at rest with solenoids B, E and H energized. All of thegized from the normally closed contacts of relay R through conductorI22. Solenoid D is not energized through the normally closed contacts ofrelay R! because the limit switch LS is open, thus breaking the circuitof conductors I28 and I30.. Solenoid E is energized through the normallyclosed contacts of relay R and conductor I42. Solenoid H is energizedthrough the norilmzlly closed contacts of relay R and conductor Sinceneither solenoid C nor solenoid D is energized, valve I8 is permitted tocenter by spring action thus bypassing the delivery of pump 10 fromdelivery conduit I38 through port 38, through the central bore of spool34 and through tank port 40 and conduit 6.4 to tank. The energizetion ofsolenoid E holds the spool 46 of valve I8 to the right, but since nopressure is available in conduit 68 no flow takes place through thevalve I8. Similarly because solenoid H is ener gized the spool of valve20 is shifted to the left but this merely connects pressure port 68 tothe plugged cylinder port and exhausts the motor conduit 58 to the tankconduit 84.

When it is desired to start a complete operating cycle of the threemotors I0, I2 and I4 in sequence, the starting switch I40 is depressedR. energized solenoid C through conductor I26.

Accordingly the spool of valve I6 is shifted to the right admittingpressure oil from port 38 to the motor conduit 44 and causing the pistonof motor I0 to descend. This condition of operation is holding relaysare at this- .time deenergized, and thus solenoid B is mer- I dition atthis time.

conductor I44. The spool 46 of valve I8 accordingly shifts to the leftadmitting pressure oil from port 48 to conduit 52 thus moving thepistonof motor I2 downwardly, which condition appears in line 3 of the table.

It will be noted at this time that both motors ent invention by theprovision of the auxiliary pump I8 which,- at the present stage of thecycle, is delivering oil through delivery conduit 80, branch 88, ports90 and I of valve 92, conduit I02 to conduit 44 and the head end ofmotor I0. Thus the delivery of pump I8 is directed to motor I0 andcannot pass back through delivery line 68 due to the check valve I4.This constant the valves 92, I8-and to the opposite position smalldelivery is fed into motor I0 at whatever I rate is necessary to make upfor any leakage losses in that portion of the circuit, the remainder ofthe delivery of pump I8 being bypassed over the relief valve I04 andthrough conduit I08 to the motor conduit 52 and motor I2. It should benoted before proceeding that during the downward movement 01' the pistonof motor I0 the full delivery of pump 18 was directed into the head endof motor I0 to add to the delivery of pump I0 and thus slightly increasethe speed of action thereof.

As soon as the piston 01' motor l2 completes its stroke to the bottom,the limit switch LS is contacted thus establishing the pick-up circuitfor relay R through conductors I60 and I58, relay R at this timeremaining energized. Relay R immediately holds up due to the closure ofadmitting pressure oil from conduit 88 through port 66 and conduit 50 tothe head end of motor I4, as shown in line 4 of the table. The piston ofmotor I4 accordingly rises and would, but for the pump I8, determine themaximum pressure in the delivery conduit 88 and at the motor I2. Checkvalve I8, however, prevents backflow of the delivery of pump I8 to thedelivery conduit 68 of pump 10 so that the delivery of pump I8 isdirected into cylinder I2 to maintain pressure therein and make upleakage losses the same as it did in cylinder I0 previously. At the sametime the pump I8 also continues to make up losses and maintain pressurein motor I0. Any excess volume above the combined requirements of motorsI0 and I2 is bypassed to tank at relief valve 8 I.

When the piston of motor l4 reaches the upper limit of its stroke limitswitch LS is opened thereby breaking the holding circuits of relays R Rand R. These'relays drop deenergizing solenoids A, F and G,respectively, and energizing solenoids B, E and H. It will be noted thatthe relay R does not drop at this time even though its holding circuitbe opened at relay R and conductor I84 because the parallel circuitthrough conductor I32 and LS is in'closed con- According y, solenoid Cremains energized.

The energization of solenoids B, E and 'H shifted as illustrated in thefifth line of the table of Figure 2. Accordingly the delivery or pump I0is directed through check valve 18, port 48 andconduits 54 and 58 to therod end of motor I2 and also to the rod end of motor I4. Since thelatter has the advantage of a gravity bias'it descends first dischargingoil from the head end through conduit 56 and port 00 to tank conduit 64.When this stroke has been completed the pump delivery will then bedirected to the rod end of cylinder I2 raising the piston thereof andopening the limit switch LS This has no effect, however, since thecircuit I58-I60 was already opened by dropping of the relay R Shiftingof valve 82 directed the delivery from pump I8 to motor port IIO throughconduit H2 and check valve H8 to the conduits 54 and 58, thus adding thedelivery of pump I8 to that of the pump I0 in retracting the motors I2and I4. I

When the piston of motor I2 reaches the upper limit of its stroke, limitswitch LS is opened thus breaking the holding circuit for relay Rpermitting the latter to drop which deenergizes solenoid C and energizessolenoid D. The spool 84 of valve I8 is accordingly shifted completelyto the left directing the delivery from pump I0 through port 38 andmotor conduit 42 to the rod end of motor l0, as shown inline 8 of thetable. The piston of the latter accordingly rises and the pump I8maintains pressure on the rod end of cylinders I2 and I4. Any excessdelivery not required at these motors passes over the relief valve H4and through conduit II8 to the motor conduit 42 thus adding to thedelivery of pump I0 in raising the piston of motor I0. When the lattercompletes its stroke, limit switch LS is opened thus breaking thecircuit I28-I80 of solenoid D and permitting the spool 34 of valve I8 toreturn to center position under the action of the spring 36. The partsare thus restored to their original position.

.Check valve I06 prevents discharge from the head end of motor I0 whilethe motors I2 and I4 are returning at which time the conduit 44 wouldotherwise be open to tank through conduit I02 and ports I00 and 94 ofvalve 02. Similarly the check valve II6 prevents flow of pressure oil totank from the rod end of cylinders I2 and I4 while the piston of motorI0 is descending.

While the form of embodiment of the invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollowWhat is claimed isv as follows:

1'. In a hydraulic ,power transmission system having a plurality ofreversible fluid motors operablein sequence, a main pump and supplyconduit for supplying fluid to each of. the motors, directional controlvalves, one for each motor, connected to said supply conduit inparallel, an

auxiliary pump for supplying sufflcient fluid to one of said motors tomaintain full working pressure therein independently of the main pumpwhile the main pump is supplying fluid to another motor, means forpreventing back flow -from said one motor to the main pump while put ofthe auxiliary pump to either of said auxiliary supply conduits.

2. In a hydraulic power transmission system having at least three fluidmotors operable in sequence, a main pump and supply conduit forsupplying fluid to each oft-the motors, directional control valves, onefor each motor, connected to said supply conduit inparallel, .anauxiliary pump for supplying sufflcient flui to two of said motors tomaintain full working pressure thereon independently of the main pumpwhile the main pump is supplying fluid to another motor, means forpreventing back flow from said two motors to the main pump while beingsupplied from the auxiliary pump, an auxiliary supply conduitunrestrictedly open to flow from the auxiliary pump to one of said twomotors, means connecting the auxiliary pump to the auxiliary supplyconduit, a branch supply conduit leading to the other of said twomotors, and apressure responsive sequence valve connected to cut oiIsaid branch supply conduit from the auxiliary supply conduit atpressures therein below a predetermined value.

'3. In a hydraulic power transmission system having at least threereversible fluid motors operable in sequence, a main pump 7 of themotors, directional control valves, one ton each motor, connectedto'said supply conduit in parallel, an auxiliary pump for supplyingsufficient fluid to two of said motors to maintain full working pressurethereon independently of the main pump while the main pump is supplyingfluid to another motor, means for preventing back flow from said twomotors to the main pump while being supplied from the auxiliary pump, anauxiliary supply conduit unrestrictedly open to flow from the auxiliarypump to one of said two motors, a branch supply conduit leading to theother of said two motors, a pressure responsive sequence valve connectedto out i! said branch supp y conduit from the auxilia supply conduit atpressures'therein below a predetermined value, a second auxiliary supplyconduit, branch supply conduit, and sequence valve, similar to thefirst, and connected for reverse operation of said two motors, and adirectional control valve for selectively delivering the output of theauxiliary pump to either of said auxiliary supply conduits.

and su plylcon-v .duit tor supplying fluid to each

